Enhanced energy transfer and multimodal vibration mitigation in anelectromechanical acoustic black hole beam

Owing to their unique energy focusing capability and high-frequency damping effects, AcousticBlack Hole (ABH) structures show promise for numerous engineering applications. However, conventionalABH structures are mostly effective only above the so-called cut-on frequency, a bottlenecking deficiency thatneeds to be addressed if low-frequency problems are of concern. Meanwhile, achieving simultaneous highfrequency ABH effects and low-frequency vibration reduction is also a challenge. In this paper, electrical linearand nonlinear shunts are intentionally added to an ABH beam via PZT patches to tactically influence itsdynamics through electromechanical coupling. Both numerical and experimental results confirm that theeffective frequency range of the ABH can be broadened as a result of the electrical nonlinearity induced energytransfer (ET) from low to high frequencies inside the beam. However, increased nonlinearity strength, albeitbeneficial to energy transfer, jeopardizes the linear dynamic absorber (DA) effects acting on the lower-orderresonances. Solutions are exploited to tackle this problem, exemplified by the use of negative capacitance inthe nonlinear shunts with the embodiment of parallel linear electrical branches. On top of the nonlinear ETeffects, simultaneous DA effect is also achieved for the low-frequency resonant vibration mitigation. Studiesfinally end up with a design methodology which embraces the principle of ET and DA to tactically cope withdifferent frequency bands. The final outcome is the broadband multi-modal vibration reduction and thebreaking down of the frequency barrier existing in conventional linear ABH structures.